Efficacy of Influenza Vaccine in HIV Infected Adults

Vaccination of HIV infected individuals with the sub-unit influenza vaccine is safe; however it induces only moderate immune responses and likewise is modest in its protection compared to HIV uninfected individuals. Based upon the available data, the South African Thoracic Society has provisionally recommended the use of influenza vaccine in HIV infected individuals with CD4+ counts of > 200/ml and viral loads of < 100 000 copies/ml.(Green R et al. In press, SAMJ). This proposal is however based upon recommendations made elsewhere with minimal level of evidence regarding its benefit, and no evidence from countries with a high prevalence of HIV. Very few HIV infected adults, however, actually do receive influenza vaccine in South Africa, partly because of the absence of compelling data regarding the burden of disease in Africa as well as lack of vaccine effectiveness and issues related to physician awareness and access to influenza vaccine in the public immunization program.

The conflicting evidence, between developed countries and Africa, regarding the effectiveness of PPV highlight the drawbacks of extrapolating vaccine effectiveness data from developed countries to developing countries. Differences in the epidemiology of HIV between developed countries in which the prevalence of HIV is low to that of high-burden sub-Saharan African countries include:

• differences in the mode of transmission of HIV and demographics of the infected population.
• differences in standard of care, including access to prophylaxis against opportunistic infections and use of highly active anti-retroviral therapy (HAART)
• differences in risk for disease from opportunistic pathogens, e.g. Mycobacterium tuberculosis, etc.

These differences may all contribute to differences in the risk and severity of influenza illness among HIV infected adults from these communities as well as possibly responsiveness and effectiveness of vaccination.

The investigators are conducting a double-blinded, placebo controlled randomized trial at the HIV treatment clinic at Helen Joseph Hospital to determine the effectiveness of influenza vaccination in HIV infected adults in South Africa. The significance of the findings from this study will help quantify the burden of influenza illness in African HIV infected adults, as well as assist in making more informed recommendations for the use of influenza vaccine in HIV infected adults and in guiding national policy for preparing for a future influenza virus-pandemic.